Lithium anode with multilayer composite artificial SEI film, its preparation method and application

Abstract

This invention discloses a lithium anode with a multilayer composite artificial SEI film, its preparation method, and its application, relating to the field of lithium battery technology; it includes a porous material, a lithiophilic layer, lithium metal, and an inorganic composite material; one side of the porous material is sequentially deposited with a lithiophilic layer and lithium metal, and the other side is deposited with an inorganic composite material; the porous material is at least one of porous carbon material and porous silicon material; the inorganic composite material is LiF, Li2O, Li3N, Li2CO3, Li2S, or Li 10 GeP2S 12 The invention utilizes at least five of the following: Li3PO4, Li3PO4, and Li3PO4. By constructing a lithium-loving, sponge-like porous structure, the lithium deposition space is increased, effectively suppressing the growth of lithium dendrites and preventing them from piercing the SEI layer. At the same time, a highly stable, excellent ionic conductivity, and mechanical strength artificial SEI layer is constructed using multifunctional inorganic composite materials, thereby improving the cycle performance, safety, and overall efficiency of lithium batteries.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, specifically to a lithium anode with a multilayer composite artificial SEI film, its preparation method, and its application. Background Technology

[0002] Currently, lithium metal anodes have the following problems during charge-discharge cycles, which limit the cycle life, safety, and energy density of batteries.

[0003] 1. During the charging and discharging process, lithium metal anodes often experience non-uniform lithium deposition, leading to the growth of lithium dendrites. These dendrites can not only pierce the solid electrolyte interphase (SEI) layer but may also penetrate the battery separator, causing internal short circuits. The growth of lithium dendrites is one of the main causes of battery thermal runaway and even fires and explosions, seriously affecting battery safety and cycle performance.

[0004] 2. An unstable SEI layer often forms on the surface of the negative electrode. This SEI layer continuously breaks down and rebuilds during battery charging and discharging, leading to a decrease in ionic conductivity. Naturally formed SEI layers are usually uneven in thickness and have low ionic conductivity, which cannot effectively support efficient ion migration, resulting in accelerated performance degradation of the battery under high-rate charging and discharging.

[0005] 3. Current SEI layers generally suffer from fragility and instability, failing to maintain stability during prolonged charge-discharge cycles. As the battery cycles, the SEI layer gradually breaks down and rebuilds, increasing the battery's internal resistance and leading to direct contact between the negative electrode and the electrolyte. This, in turn, triggers side reactions and accelerates irreversible lithium loss. Therefore, the structural stability of the SEI layer directly affects the battery's cycle life and efficiency.

[0006] 4. Existing SEI layers often fail to provide sufficient mechanical strength to maintain structural integrity in the face of the expansion and contraction of the negative electrode. During battery charging and discharging, the lithium metal negative electrode undergoes volume changes, which can lead to cracks and peeling of the SEI layer, further accelerating battery performance degradation. Due to the poor mechanical properties of existing SEI layers, they cannot effectively adapt to the volume changes of the lithium metal negative electrode, causing the battery to fail after multiple cycles.

[0007] The aforementioned technical defects greatly limit the practical application of lithium metal anodes. Therefore, a lithium anode with a multilayer composite artificial SEI film is proposed to solve these problems. Summary of the Invention

[0008] This invention aims to address the technical problems of lithium metal anodes in the prior art, such as lithium dendrite growth, low ionic conductivity, and poor stability and mechanical properties. The objective is to provide a lithium anode with a multilayer composite artificial SEI film, its preparation method, and its application. By constructing a lithiophilic sponge-like porous structure, the lithium deposition space is increased, effectively suppressing the growth of lithium dendrites and preventing them from piercing the SEI layer. At the same time, a highly stable artificial SEI layer with excellent ionic conductivity and mechanical strength is constructed using multifunctional inorganic composite materials, thereby improving the cycle performance, safety, and overall efficiency of lithium batteries.

[0009] This invention is achieved through the following technical solution:

[0010] The first objective of this invention is to provide a lithium anode having a multilayer composite artificial SEI film, comprising a porous material, a lithiophilic layer, lithium metal, and an inorganic composite material;

[0011] One side of the porous material is sequentially deposited with a lithiophilic layer and lithium metal, and the other side of the porous material is deposited with an inorganic composite material.

[0012] The porous material is at least one of porous carbon material and porous silicon material;

[0013] The inorganic composite material is LiF, Li2O, Li3N, Li2CO3, Li2S, Li 10 GeP2S 12 At least five of the following: Li3PO4.

[0014] Furthermore, the pore size of the porous material ranges from 50 nm to 100 nm.

[0015] Furthermore, the lithiophilic layer material is Ag.

[0016] Furthermore, the inorganic composite material is LiF, Li2O, Li3N, Li2CO3 and Li2S, Li 10 GeP2S 12 A mixture of any one of Li3PO4.

[0017] Furthermore, the mass ratio of each component in the inorganic composite material is LiF:Li2O:Li3N:Li2CO3:(Li2S or Li 10 GeP2S 12 Or Li3PO4)=(0.5-2):1:1:1:1.

[0018] The second objective of this invention is to provide a method for preparing a lithium anode with a multilayer composite artificial SEI film, comprising the following preparation steps:

[0019] After cleaning the porous material to remove organic contaminants, it undergoes nitriding treatment.

[0020] A lithiophilic material is deposited on one side of a porous material to form a lithiophilic thin film;

[0021] Deposit lithium metal on a lithiophilic layer;

[0022] An inorganic composite material is deposited on the other side of the porous material and then cooled and solidified to obtain a lithium anode with a multilayer composite artificial SEI film.

[0023] Furthermore, the cleaning of the porous material includes the following steps:

[0024] The porous material is cleaned with nitric acid or a mixed acid solution of nitric acid and sulfuric acid, then rinsed with deionized water, dried, and finally heated to 400-800℃ in an inert atmosphere to remove surface organic contaminants.

[0025] Furthermore, the nitriding treatment includes the following steps:

[0026] The porous material is immersed in urea or melamine solution, dried by stirring at 60-80℃, and then heat-treated at 600-800℃ in a nitrogen or ammonia atmosphere to introduce active nitrogen sites.

[0027] Furthermore, the deposition is performed using vacuum evaporation coating technology.

[0028] A third objective of this invention is to provide the application of a lithium anode with a multilayer composite artificial SEI film in lithium batteries.

[0029] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0030] 1. This invention enables the uniform deposition of lithium metal within a porous structure by incorporating porous materials, providing space for lithium dendrite growth and effectively preventing lithium dendrites from piercing the SEI layer. By incorporating a lithiophilic layer, a highly active lithiophilic interface is introduced to the surface of the porous material, significantly reducing the energy barrier for lithium ion migration and improving the ionic conductivity of the interface. The introduction of an inorganic composite material layer forms a robust artificial SEI layer, which not only possesses excellent chemical stability but also significantly improves the mechanical strength and lithium ion conductivity of the interface. Therefore, through the synergistic effect of these structures, the cycle performance, safety, and overall efficiency of lithium batteries are effectively improved.

[0031] 2. In the process of preparing lithium anode, the present invention can enhance surface activity by removing organic contaminants from the surface of porous materials, ensuring that lithium metal can be uniformly deposited in the porous structure and providing space for the dendrite growth of Li.

[0032] 3. In the process of preparing lithium anode, the present invention can enhance the chemical activity of porous materials by functionalizing them, strengthen their bonding with subsequent materials, and make the overall structure more adaptable to volume changes during battery cycling, reducing interlayer shedding. At the same time, it optimizes the distribution of surface active sites, which helps to improve the conduction efficiency of lithium ions in porous materials. Furthermore, after high-temperature treatment, the porous materials possess excellent mechanical strength and durability.

[0033] 4. In the process of preparing lithium anode, the present invention introduces a highly active lithium-loving interface through the evaporation coating of the lithium-loving layer, which can significantly reduce the energy barrier for lithium ion migration and improve the ionic conductivity of the interface.

[0034] 5. In the process of preparing lithium anode, the present invention forms a robust artificial SEI layer by introducing an inorganic composite material layer, which not only has excellent chemical stability, but also significantly improves the mechanical strength of the interface and the conductivity of Li ions. Furthermore, the inorganic composite material layer prepared by co-evaporation technology has high density and high uniformity, which can effectively isolate the direct contact between the lithium anode and the electrolyte, reduce interfacial side reactions, and extend the cycle life of the battery. Attached Figure Description

[0035] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings:

[0036] Figure 1 This is a schematic diagram of the structure of the sponge-like multilayer composite artificial SEI membrane of the present invention;

[0037] The attached diagram shows the markings and corresponding component names:

[0038] 1-Porous material, 2-Lithophilic layer, 3-Lithium metal, 4-Inorganic composite material. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention.

[0040] The following detailed description of embodiments of the lithium anode having a multilayer composite artificial SEI film, its preparation method, and its applications, with appropriate reference to the accompanying drawings, is provided. However, unnecessary details may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art.

[0041] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the particular range. The range defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range.

[0042] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0043] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0044] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other substances not listed may also be included, or that only the listed substances may be included.

[0045] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, but sequentially is preferred.

[0046] like Figure 1 As shown, the present invention provides a lithium anode with a multilayer composite artificial SEI film, comprising a porous material 1, a lithiophilic layer 2, lithium metal 3, and an inorganic composite material 4;

[0047] One side of the porous material 1 is sequentially deposited with a lithiophilic layer 2 and lithium metal 3, and the other side of the porous material 1 is deposited with an inorganic composite material 4.

[0048] The porous material 1 is at least one of porous carbon material and porous silicon material;

[0049] The inorganic composite material 4 is LiF, Li2O, Li3N, Li2CO3, Li2S, Li 10 GeP2S 12 At least five of the following: Li3PO4.

[0050] This invention enables the uniform deposition of lithium metal within a porous structure by incorporating porous materials, providing space for lithium dendrite growth and effectively preventing lithium dendrites from piercing the SEI layer. By incorporating a lithiophilic layer, a highly active lithiophilic interface is introduced to the surface of the porous material, significantly reducing the energy barrier for lithium ion migration and improving the ionic conductivity of the interface. The introduction of an inorganic composite material layer forms a robust artificial SEI layer, which not only possesses excellent chemical stability but also significantly improves the mechanical strength and lithium-ion conductivity of the interface. Therefore, through the synergistic effect of these structures, the cycle performance, safety, and overall efficiency of lithium batteries are effectively improved.

[0051] Preferably, the pore size of the porous material 1 is in the range of 50nm-100nm.

[0052] Preferably, the material of the lithiophilic layer 2 is Ag.

[0053] Preferably, the inorganic composite material 4 is LiF, Li2O, Li3N, Li2CO3 and Li2S, Li 10 GeP2S 12 A mixture of any one of LiF, Li2O, Li3N, Li2CO3, and Li3PO4. More preferably, the mass ratio of the components in the inorganic composite material 4 is LiF:Li2O:Li3N:Li2CO3:(Li2S or Li 10 GeP2S 12 Or Li3PO4)=(0.5-2):1:1:1:1.

[0054] The above-mentioned method for preparing a lithium anode with a multilayer composite artificial SEI film includes the following preparation steps:

[0055] S1. Cleaning porous materials to remove organic contaminants: Clean the porous materials with nitric acid or a mixed acid solution of nitric acid and sulfuric acid, wash with deionized water, dry them, and finally heat them in an inert atmosphere to 400-800℃ to remove surface organic contaminants.

[0056] This step, by removing organic contaminants from the surface of the porous material, enhances surface activity, ensuring that lithium metal can be uniformly deposited within the porous structure, and providing space for the dendrite growth of Li.

[0057] S2. Functionalization treatment: The porous material is immersed in urea or melamine solution, stirred and dried at 60-80℃, and then heat-treated at 600-800℃ in a nitrogen or ammonia atmosphere to introduce active sites such as pyridine nitrogen and pyrrole nitrogen, thereby achieving nitridation treatment.

[0058] Alternatively, the functionalization process can also involve oxidation: immersing porous carbon in a hydrogen peroxide solution and stirring at 70°C for 2 hours increases the number of oxygen-containing functional groups on the surface, enhancing hydrophilicity and affinity with other materials.

[0059] Nitriding involves immersing porous materials in a urea or melamine solution while heating and stirring to promote the evaporation of water from the solution. This dries the surface of the porous material and fixes the urea or melamine, which helps to coat the material evenly and avoids uneven deposition.

[0060] This step, through functionalization, can enhance the chemical activity of porous materials, strengthen their bonding with subsequent materials, and make the overall structure more adaptable to volume changes during battery cycling, reducing interlayer shedding. At the same time, it optimizes the distribution of surface active sites, which helps to improve the lithium-ion conduction efficiency in porous materials. Furthermore, after high-temperature treatment, the porous materials possess excellent mechanical strength and durability.

[0061] S3, Lithophilic layer evaporation coating: Using vacuum evaporation coating technology, a lithophilic material is deposited on one side of the porous material to form a lithophilic layer film.

[0062] This step introduces a highly active lithiophilic interface through the evaporation coating of the lithiophilic layer, which can significantly reduce the energy barrier for lithium ion migration and improve the ionic conductivity of the interface.

[0063] S4, Li metal evaporation coating: Lithium metal is deposited on a lithiophilic layer using vacuum evaporation coating technology to form a stable lithium anode.

[0064] S5. Co-evaporated inorganic composite material: The components of the inorganic composite material are fully mixed in proportion to form an inorganic composite material. Vacuum evaporation coating technology is used to deposit the inorganic composite material on the other side of the porous material to form a strong SEI layer. After cooling and curing, a lithium anode with a multi-layer composite artificial SEI film is obtained.

[0065] This step introduces an inorganic composite material layer to form a robust artificial SEI layer, which not only has excellent chemical stability but also significantly improves the mechanical strength of the interface and the conductivity of Li ions. Furthermore, the inorganic composite material layer prepared by co-evaporation technology has high density and high uniformity, which can effectively isolate the direct contact between the lithium anode and the electrolyte, reduce interfacial side reactions, and extend the cycle life of the battery.

[0066] In summary, this invention constructs a lithium-loving, sponge-like porous material layer to increase lithium deposition space, effectively suppressing lithium dendrite growth and preventing it from piercing the SEI layer. By introducing inorganic composite materials, it constructs an artificial SEI layer with high stability, excellent ionic conductivity, and mechanical strength, significantly reducing the frequency of repeated formation and breakage of the SEI layer, minimizing irreversible lithium metal loss, and improving the battery's coulombic efficiency and capacity retention. At the same time, it effectively blocks the growth path of lithium dendrites, enhancing the overall safety of the battery, making it particularly suitable for high-energy-density applications.

[0067] The technical solution of the present invention will be further described in detail below with reference to the embodiments.

[0068] It should be noted that, unless otherwise specified, the experimental methods used in the embodiments are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0069] Example 1

[0070] A method for preparing a lithium anode with a multilayer composite artificial SEI film includes the following preparation steps:

[0071] S1: Pretreatment of porous carbon materials

[0072] The porous carbon material (pore size of about 70 nm) was placed in a 20% mixed acid (a 1:1 mixture of nitric acid and sulfuric acid) and stirred and refluxed for 2-4 hours to ensure the surface of the material was clean. Then it was washed several times with deionized water until neutral and dried. Finally, the porous carbon was heated to 600°C and held at that temperature for 2 hours under an inert atmosphere (nitrogen) to remove organic contaminants from the surface.

[0073] S2: Functionalization

[0074] Prepare a urea solution and immerse the porous carbon material in the solution. Stir and dry at 60-80℃. Then, heat-treat the immersed porous carbon material in a nitrogen atmosphere at 700℃ for 2 hours to introduce active nitrogen sites.

[0075] S3: Lithophilic layer evaporation coating

[0076] The treated porous carbon was fixed 25 cm above the crucible, and the lithiophilic material (Ag) was placed inside the crucible. The vacuum environment was controlled at 10 °C. -5 Pa, crucible heating power is 200W, evaporation rate is Ag is deposited on the surface and inside the pores of porous carbon to form a lithiophilic thin film.

[0077] S4: Li metal evaporation coating

[0078] A porous carbon material with a deposited lithophile layer was placed 25 cm above the crucible, and a Li foil was placed inside the crucible. The temperature of the heating source and the evaporation rate were controlled to keep the Li foil in a vacuum environment (10). -5 Pa) was deposited onto the surface of the lithiophilic layer. The crucible heating power was 300W, and the evaporation rate was...

[0079] S5: Preparation of Inorganic Composite Materials

[0080] A composite material of LiF, Li2O, Li3N, Li2CO3, and Li2S was prepared by mixing these materials in a mass ratio of 1:1:1:1:1, and then the inorganic composite material was added into a crucible in a vacuum chamber.

[0081] S6: Co-evaporation deposition of inorganic composite materials

[0082] The other side of the porous material was fixed 25 cm above the crucible, and the temperature of the heating source and the evaporation rate were controlled to allow the inorganic composite material to be heated in a vacuum environment (10). -5 The material is sublimated (Pa) and deposited as a thin film on the other side of the porous material. The crucible heating power is 250W, and the evaporation rate is...

[0083] S7: Cooling and curing

[0084] The deposited inorganic composite SEI layer is allowed to cool and solidify naturally. The solidified film is firmly bonded to the surface of the porous carbon material, forming a stable inorganic composite SEI layer, thus obtaining a lithium anode with a multilayer composite artificial SEI film.

[0085] Example 2

[0086] The difference between this embodiment and Embodiment 1 is that the porous carbon material in steps S1-S3 is replaced with porous silicon material with a pore size of about 70nm, while the others remain unchanged.

[0087] Example 3

[0088] The difference between this embodiment and Embodiment 1 is that the porous carbon material in steps S1-S3 is replaced with a porous Si / C composite material with a pore size of about 70 nm, while the others remain unchanged.

[0089] Example 4

[0090] The difference between this embodiment and Embodiment 1 is that the inorganic composite material in step S5 is replaced with LiF:Li2O:Li3N:Li2CO3:Li 10 GeP2S 12 =1:1:1:1:1, everything else remains the same.

[0091] Example 5

[0092] The difference between this embodiment and Embodiment 1 is that the inorganic composite material in step S5 is replaced with LiF:Li2O:Li3N:Li2CO3:Li3PO4 = 1:1:1:1:1, while other aspects remain unchanged.

[0093] Example 6

[0094] The difference between this embodiment and Embodiment 1 is that the inorganic composite material in step S5 is replaced with LiF:Li2O:Li3N:Li2CO3:Li2S = 2:1:1:1:1, while other aspects remain unchanged.

[0095] Comparative Example 1

[0096] The difference between this comparative example and Example 1 is that: porous materials are not used, and the inorganic composite material is replaced with a single LiF. During preparation, Li foil is used directly, and after cleaning, LiF is directly vapor-deposited onto the Li foil.

[0097] Comparative Example 2

[0098] The difference between this comparative example and Example 1 is that: porous materials are not used, and the inorganic composite material is replaced with a single Li3N. During preparation, Li foil is used directly, and after cleaning, Li3N is directly vapor-deposited onto the Li foil.

[0099] Comparative Example 3

[0100] The difference between this comparative example and Example 1 is that: porous materials are not used, and the inorganic composite material is replaced with a single Li2O. Li foil is used directly during preparation, and after cleaning, Li2O is directly vapor-deposited onto the Li foil.

[0101] Comparative Example 4

[0102] The difference between this comparative example and Example 1 is that no lithiophilic layer is provided on the surface of the porous material.

[0103] Comparative Example 5

[0104] The difference between this comparative example and Example 1 is that the porous material is not nitrided.

[0105] The lithium anodes prepared in Examples 1-6 and Comparative Examples 1-5 were tested.

[0106] Button cells were assembled and tested: the negative electrode was a lithium negative electrode obtained in the examples / comparative examples, and the positive electrode was LiFePO4. The diameter of the lithium iron phosphate positive electrode was 12 mm, and the average load was approximately 2 mg cm⁻¹. -2A separator (Celgard 2400) was placed between the two electrodes. The CR2032 coin cell was assembled in an argon-filled glove box (U-Super MK4306-000-00, mikroua Technology Co., Ltd.). The electrolyte was a carbonate-based electrolyte (1.0 mol l⁻¹ LiPF₆, with ethyl carbonate (EC) / diethyl carbonate (DEC) as the solvent, volume ratio 1:1). All charge / discharge tests were performed using a battery cycler (MIHW-200-160CH, Neware Technology Ltd.). Each charge / discharge cycle was fixed at 1 hour, and after 3 activation cycles at 0.2C, the cells were discharged from 2.5 to 4.2V (1C = 170 mAg). -1 Tests were performed within the voltage window of the test. Electrochemical impedance spectroscopy (EIS) was performed using an electrochemical workstation (AutoLabPGSTAT302N, Metrohm) with a frequency range of 1×10⁻⁶. 6 Up to 0.01Hz, the AC disturbance intensity is 5mV.

[0107] The test results are shown in Table 1.

[0108] Table 1. Test data for examples and comparative examples

[0109] project Loop count Capacity retention Example 1 800 91.13％ Example 2 800 90.71％ Example 3 800 89.88％ Example 4 800 89.33％ Example 5 800 87.16％ Example 6 800 88.79％ Comparative Example 1 800 77.84％ Comparative Example 2 800 77.83％ Comparative Example 3 800 76.71％ Comparative Example 4 800 74.92％ Comparative Example 5 800 74.13％

[0110] As can be seen from the data in Table 1, the lithium anode prepared in the embodiment of the present invention can retain more than 87% of its capacity after 800 cycles, exhibiting excellent cycle performance. In contrast, the capacity retention rate of the comparative example after 800 cycles is significantly lower than that of the embodiment of the present invention. Therefore, the present invention can improve the cycle performance, safety, and overall efficiency of lithium batteries.

[0111] Regarding mechanical strength, the Poisson's ratio of the inorganic composite material in Example 1 is 0.17, while that of the single LiF material in Comparative Example 1 is 0.2. The lower the Poisson's ratio, the better the material stiffness. Therefore, the present invention forms a robust artificial SEI layer by introducing an inorganic composite material layer, which can effectively improve the mechanical strength of the interface.

[0112] Regarding Li ion conductivity, the Li ion migration barrier of the inorganic composite material in Example 1 is 0.13, while that of the Li ion migration barrier of the single LiF material in Comparative Example 1 is 0.17. The lower the migration barrier, the higher the Li ion conductivity. It can be seen that the present invention can effectively improve Li ion conductivity by introducing an inorganic composite material layer to form a robust artificial SEI layer.

[0113] Finally, it should be noted that the above specific embodiments are only used to describe the purpose, technical solution, and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation of the present invention and is not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the foregoing specific embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions or improvements can be made to some or all of the technical features. These modifications, equivalent substitutions, and improvements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered within the scope of the claims and specification of the present invention.

Claims

1. A lithium anode with a multilayer composite artificial SEI film, characterized in that, It includes porous materials (1), lithiophilic layers (2), lithium metal (3), and inorganic composite materials (4); One side of the porous material (1) is sequentially deposited with a lithiophilic layer (2) and lithium metal (3), and the other side of the porous material (1) is deposited with an inorganic composite material. The lithiophilic layer (2) is made of Ag; The porous material (1) is at least one of porous carbon material and porous silicon material; The inorganic composite material (4) is LiF, Li2O, Li3N, Li2CO3 and Li2S, Li 10 GeP2S 12 A mixture of any one of Li3PO4; The preparation method includes the following steps: After cleaning the porous material to remove organic contaminants, it undergoes nitriding treatment. A lithiophilic material is deposited on one side of a porous material to form a lithiophilic thin film; Deposit lithium metal on a lithiophilic layer; An inorganic composite material is deposited on the other side of the porous material and then cooled and solidified to obtain a lithium anode with a multilayer composite artificial SEI film.

2. The lithium anode with a multilayer composite artificial SEI film according to claim 1, characterized in that, The pore size of the porous material (1) is in the range of 50nm-100nm.

3. The lithium anode with a multilayer composite artificial SEI film according to claim 1, characterized in that, The mass ratio of each component in the inorganic composite material (4) is LiF : Li2O : Li3N : Li2CO3 : (Li2S or Li 10 GeP2S 12 Or Li3PO4)=(0.5-2):1:1:1:

1.

4. The lithium anode with a multilayer composite artificial SEI film according to claim 1, characterized in that, The cleaning of porous materials includes the following steps: The porous material is cleaned with nitric acid or a mixed acid solution of nitric acid and sulfuric acid, then rinsed with deionized water, dried, and finally heated to 400-800℃ in an inert atmosphere to remove surface organic contaminants.

5. The lithium anode with a multilayer composite artificial SEI film according to claim 1, characterized in that, The nitriding treatment includes the following steps: The porous material is immersed in urea or melamine solution, dried by stirring at 60-80℃, and then heat-treated at 600-800℃ in a nitrogen or ammonia atmosphere to introduce active nitrogen sites.

6. The lithium anode with a multilayer composite artificial SEI film according to claim 1, characterized in that, The deposition was performed using vacuum evaporation coating technology.

7. The application of the lithium anode with a multilayer composite artificial SEI film as described in any one of claims 1-6 in a medium-sized lithium battery.

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